Remotely operated door locks are often used to provide security controlled access to offices, home units, banks and other buildings requiring access control.
Such door locks typically consist of a retractable spring biased latch bolt fitted to the edge of the door and a latching strike assembly fitted to the doorjamb. A latching strike positioned at the edge of a recess defined in the body of the latch strike assembly is pivotally displaceable between a closed position retaining the latch bolt within the recess and an open position releasing the latch bolt from the recess. The latch bolt retracts and rides over the edge of the latching strike and into the recess upon closing of the door. A locking means, typically in the form of a pin or set of pins or system of levers, is operated by way of a solenoid to lock the latching strike in the closed position to thereby lock the latch bolt within the recess and thereby retain the door in a locked state.
The presently available door locks as described above utilise a single solenoid to move the locking means between the locked and unlocked positions. The door locks are provided in one of two configurations. In the first ‘fail safe’ configured type of lock the locking means is maintained in the locking position when the solenoid is energised and in the unlocking position when the solenoid is not energised, providing a fail safe operation of the door lock, ensuring the door is unlocked when there is a power failure de-energising the solenoid. In the second ‘fail secure’ configured type of lock the locking means is maintained in the unlocking position when the solenoid is energised and in the locking position when the solenoid is not energised, providing a fail secure operation of the door lock, ensuring the door is locked when there is a power failure. In both of these configurations only one or the other of the locking and unlocking positions is a stable state.
These door locks require a constant power supply and energising of the solenoid to keep the locking means in either of the locked or unlocked positions (depending upon whether a fail safe or fail secure configuration). As a result of this power requirement, which is usually backed by a back up battery power supply to ensure continuous operation, these systems generally use a centralised electronic control system requiring significant wiring and infrastructure. Accordingly, these systems are not particularly suitable for small to medium buildings such as residential, small businesses, old style dwellings and multiple buildings that are difficult or expensive to cable back to a central system.